Monday, June 15, 2009

The Lead Investigator Responds

In a prior post, the Disease Management Care Blog raised some questions about a wonderful study about 'PAM' conducted in two LifeMasters call centers.

As readers may recognize, comments in the Google system are buried away from the main blog page: the post itself needs to be accessed and the comments will only then appear at the bottom.

In this instance, the DMCB heard directly from the principal author of the study. Her timely and helpful response deserves greater visibility. It is reproduced in it's entirety here:

Thank you for your review of our recent study. As the lead investigator on the study, I am happy answer the questions you raised about the methodology. You asked if hospitalization risk was part of the propensity score risk adjustment we used to equalize the two study groups. Yes, the risk severity score, based on claims data, was part of the risk adjustment approach. You also asked about the differences in hospitalization rates between the two groups. The analytic approach we used assessed the trajectory of change and examined whether this trajectory was different for the intervention group as compared to the control group. This analytic approach reduced the need to control for multiple factors, because most of the characteristics of the individuals remained fixed and changes that were observed could be attributed to the intervention. However, because there were some key differences at baseline (including their baseline utilization rates), we constructed the propensity weights to equalize the 2 groups. That is to say, after controlling for other differences, the statistical significance in the utilization tables indicates that the trajectory of change significantly differed for the intervention group as compared to the control group. In the case of Emergency Department use, the control group’s trajectory was up, while the intervention group was down. In the case of hospitalizations, the control group trajectory was flat, while the intervention group went down.Finally you asked about a possible Hawthorne effect, with the nurses who were responding to this “observation” rather than the PAM intervention. This is a very unlikely explanation, as both the intervention nurses and the control group nurses knew they were in a study and were being observed, thus the effect of “observation,” would have been the same for both groups of nurses.

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